/*eslint-disable*/
const originaltoFixed = Number.prototype.toFixed;
Number.prototype.toFixed = function (n) {
  if (n > 20 || n < 0) {
    throw new RangeError('toFixed() digits argument must be between 0 and 20');
  }
  const number = this;
  if(number.toString().length>=21){
    // 如果是科学计数法  返回浏览器原有的处理方式
    return originaltoFixed.call(this,n);
  }
  if (isNaN(number) || number >= Math.pow(10, 21)) {
    return number.toString();
  }
  if (typeof (n) === 'undefined' || n == 0) {
    return (Math.round(number)).toString();
  }

  let result = number.toString();
  const arr = result.split('.');

  // 整数的情况
  if (arr.length < 2) {
    result += '.';
    for (let i = 0; i < n; i += 1) {
      result += '0';
    }
    return result;
  }

  const integer = arr[0];
  const decimal = arr[1];
  if (decimal.length == n) {
    return result;
  }
  if (decimal.length < n) {
    for (let i = 0; i < n - decimal.length; i += 1) {
      result += '0';
    }
    return result;
  }
  result = `${integer}.${decimal.substr(0, n)}`;
  const last = decimal.substr(n, 1);

  // 四舍五入，转换为整数再处理，避免浮点数精度的损失
  if (parseInt(last, 10) >= 5) {
    const x = Math.pow(10, n);
    let curnum = 1;
    if(result<0){
      curnum = -1;
    }
    result = (Math.round((parseFloat(result) * x)) + curnum) / x;
    result = result.toFixed(n);
  }

  return result;
};


/* eslint-enable */
